An important component of absorbent articles such as diapers, sanitary napkins, pantiliners, incontinent pads, breast pads, perspiration pads, an the like, is an absorbent core structure that includes absorbent materials, such as water-absorbing polymeric particles, typically hydrogel-forming water-swellable polymers, also referred to as absorbent gelling material (“AGM”), or super-absorbent polymers (“SAP”). These absorbent materials ensure that large amounts of fluids, e.g. urine, can be absorbed by the article during its use and locked away, thus providing low rewet and good skin dryness, thereby reducing wearer discomfort.
Different absorbent articles may be designed with different spatial patterns, or distributions, of AGM within their absorbent core structures, depending, for instance, on the nature and/or the intended use of the absorbent articles. For example, diapers intended for boys may have a different distribution of AGM than those intended for girls. Differences in the distributions of AGM may include variations in the shapes of AGM distribution (e.g., rectangular, elliptical, and so on), discrepancies in the overall densities of AGM (or densities in particular regions) and/or in the density transitions between different regions of the absorbent core structure. Differences in the distributions of AGM may further include differences in the absolute quantities of AGM, in the bias, or evenness, of the AGM (e.g., quantity of AGM in the front portion of the absorbent article relative to the back portion). A variety of other factors may contribute to the difference in the distribution of AGM in different absorbent articles, including the amount of AGM laminate, AGM scatter, etc.
Because different absorbent articles may be designed with different spatial distributions of AGM within their absorbent core structures, it is often desired to evaluate the distribution of AGM in a particular absorbent article. For example, the distribution of AGM may be evaluated for quality control purposes during manufacturing (e.g., to ensure that absorbent articles are produced to meet or exceed certain requirements). Additionally, or alternatively, evaluation of the distribution of AGM may be performed in a product and/or process development context, for instance, to develop more optimal techniques for distributing AGM within a particular type of absorbent article.
In the past, distribution of AGM within a given absorbent article could be evaluated in a number of ways. For example, quality control personnel could physically feel for a presence or an absence of AGM in different regions of the absorbent article with their fingers and roughly estimate the distribution of AGM. In some cases, the absorbent article could be passed through some sort of a capacitive sensor, and the amount of AGM in different portions of the absorbent article could be approximated based on the capacitance of the different portions.
The absorbent article could also be cut open, and various sections of the cut-up absorbent article could be examined under a microscope to identify the distribution of AGM in the various sections. The various sections could also be weighed, and the quantity of AGM in each section could be estimated based on the respective weights of the sections.
Traditional methods of evaluating the distribution of AGM in an absorbent article present a number of problems. Results yielded by these methods are typically imprecise, inconsistent, or both. For example, the test that involves physically feeling for the presence or absence of AGM with fingers may yield different results based on who is doing the testing. Furthermore, given that a granule of AGM is roughly the same size as a grain of salt, a person's fingers may not be sensitive enough to provide a sufficiently accurate estimation. The same may be said regarding capacitive sensors.
With regard to methods that involve cutting the absorbent article into several sections, these methods may provide information regarding distribution of AGM among the different sections, but they might not provide helpful information regarding the distribution of AGM within the individual sections. For example, if the absorbent article is cut into three sections, and each section has roughly the same weight, it does not necessarily mean that the AGM is distributed uniformly within each section. Furthermore, cutting up the absorbent article may disrupt the original distribution of AGM and, thus, make it difficult, if not impossible, to determine the original AGM distribution. Still further, cutting up the absorbent article typically means eliminating that absorbent article from production, and that may be undesirable, for example, in the context of an inline manufacturing process.